Many laboratories and research facilities today work with biological materials. This field is not only scientifically significant, but also of appreciable economic value.
When separation of biological material is required, the material is spun in a centrifuge. For small quantities of material, the spinning is accomplished in a small tubular container, referred to as a microcentrifuge tube.
Since the fluid with suspended solids is being spun, it is desirable to seal the tube to prevent spillage. Various methods and devices have been tried in the prior art to accomplish the effective sealing of the container.
Some devices make use of a threaded cap, such as that disclosed in U.S. Pat. No. 3,032,225 issued to S. Harding. The Harding device envisions the use of a gasket type element in conjunction with the cap to accomplish the seal.
Another type of device makes use of a separate frictional plug element to seal the open end of the centrifuge tube. Disclosures of this type of device are revealed in two patents issued to Donald Webster, U.S. Pat. Nos. 4,166,573 and 4,222,513.
An improvement as to convenience can be found in devices considering a container with an attached cap. Examples are the devices of Robert Hazard, U.S. Pat. No. 3,877,598, and Yung et al, U.S. Pat. No. 3,860,135. Both of these devices are intended to be used as safety containers, popularly known as "child-proof".
The other microcentrifuge tubes that are currently available on the market accomplish the seal between cap and tube strictly on the basis of friction-fit. The tightness of the fit varies with brand, and is dependent upon the envisioned usage. A tight fit is used if the samples are to be boiled, shipped, or frozen while a looser fitting type is used if the tubes are to be repeatedly opened and closed.
None of these prior art devices completely fulfill the needs of the person seeking an efficient, adaptable microcentrifuge tube. Devices such as those of Harding and Webster, which use multiple components, while effective, are cumbersome to use. Unitary devices like those of Hazard and Yung are more efficient, but are not easily handles.
In sum, the cap/tube seals of the prior art, particularly the friction fit devices, suffer from one or both of two basic disadvantages: (1) If the seal is very secure, it is relatively difficult to open and close the tube, requiring both hands or a special tool. (2) If the seal is looser, it is insufficient when the tube is stressed, as when being boiled, frozen, or shipped.